Field of the Invention
This invention relates to mechanical handling apparatus and, in its broadest aspect, it aims to provide an improved mechanical handling device for use with any machine or plant which is operating upon workpiece and wherein from time to time it is necessary to remove a treated workpiece and replace it at the same station with a fresh untreated workpiece.
More particularly, the mechanical handling device has been developed for the purpose of handling billets which are being heated in a furnace for a forging operation and wherein the device is used for loading cold billets into the furnace and taking away hot billets which are to be used in the forging process. Hereinafter, the invention is described in more detail in relation to this particular use but it will be appreciated that scope for the invention is not limited to this particular application as hereinafter described but may find application for use generally in connection with the handling of workpiece in plant, machinery and other operations outside the field of forging.
For many years hitherto it has been the practice to use an indexing rotary hearth furnace with mechanical handling devices for loading and unloading relatively large billets which are to be heated in the furnace for subsequent forging operations. In plan view such rotary hearth furnace is of circular form with the billets being arranged in spaced apart relationship and radially in relation to the vertical axis of rotation of the rotary hearth and it has been customary to use two mechanical handling devices, one for loading in cold billets and the other for unloading hot billets, each of these having automatically operating gripping tongs which grip and release a billet in a manner similar to blacksmiths' tongs, these gripping tongs being mounted on power-operated carriages which travel inwardly and outwardly in a radial direction in relation to the rotary hearth, one performing the loading of cold billets and the other performing the unloading of heated billets. This requires the furnace to have two separate doors at one side of its circumference with the two machines spaced apart so that there is, in between the two doors a "dead" zone in the furnace which is not utilised.